1. Field of the Invention
A device for distributing and redirecting light in association with photographic devices and, more particularly, to a diffuser having a prism for directing light onto a subject, particularly for use in macro photography.
2. Description of the Related Art
Macro photography commonly refers to close-up photography. Photographing subjects in close proximity requires positioning of the camera lens near the subject. However, in order to obtain the necessary magnification, the lens must be as far away from the film plane as possible. Methods of doing this generally include the use of extension tubes, bellows, close-up filters, and macro lenses, typically having the shape of a cylinder referred to as a barrel. A lens is mounted on one end of the barrel and focusing requires a simple twist of the lens barrel to move the lens element away from the film plane. Generally, macro photography presents challenges for lighting the subject.
FIG. 1 illustrates a typical flash camera 10 having a camera body 12 to which is attached a lens 14. The lens 14 is generally cylindrically shaped having a first end 16 attached to the body 12 and a second free end 18 projecting out from the camera 12, usually at a 90° angle to which is attached a lens element 15. The lens 14 may be removably attached or integrally formed with the camera body 12.
A flash unit 20 is associated with the camera 10 to provide additional illumination in low light or dark conditions. Many cameras have built-in flash units on the front 22 of the camera 12, while other cameras have the flash unit 20 removably mounted on the camera body 12. The construction and operation of these flash units 20 will not be described in detail herein because the same are readily commercially available.
Briefly, the flash unit 20 is physically and electrically coupled to the camera shutter actuator mechanism 24 to provide a timed flash of light towards the subject of the photograph so that desired illumination is present at the time the shutter opens and until the shutter closes. Most camera models provide little to no control over the direction, duration, and timing of the flash. As such, these general purpose cameras and flash units are designed for illumination of subjects that are more than twelve inches away from the end 18 of the camera lens element 15.
Attempts to use conventional camera flash units for macro photography result in inadequate lighting of the subject. FIG. 2 illustrates the effect of inadequate lighting conditions. In FIG. 2, the center 26 of the subject 28 is dark because the lens 14 protrudes into the field of illumination from the flash unit 20, casting a shadow on the subject 28 and creating the dark spot on the final image. In other cameras, the flash is concentrated in the area directly in front of the lens 14, causing over-lighting conditions and washing out of the final image. Attempts to overcome these disadvantages include the development of ring flashes for close-up photographic work. FIG. 3 illustrates a commercially-available ring flash 40 utilizing eight small built-in LED's 42 spaced equidistantly around an opening 44 that is placed over the lens 46 of the camera 48, as shown in FIG. 4. While the object of this device is to provide more even illumination on a subject, there are several disadvantages to the use of this device. First, the ring flash may block a flash sensor in the camera. Second, this device does not provide adequate illumination to the subject due to the limited power output of the light source. Third, the light amplitude is constant and cannot be modulated to provide the necessary illumination for the photograph. Conventional ring flashes that have the ability to modulate the light intensity are limited to a small number of high-end camera models and are expensive. In general, they employ complex circuitry for determining light output for proper exposure of the photograph and for interfacing with the camera. Such complex circuitry are bulky and require an independent power source.
Hence, there is a need for a method and device that distributes the light from a conventional flash unit on to a subject in a manner that enables flash macro photography without having to replace or tamper with the existing flash unit.